Energy assessment of enhanced fixed low concentration photovoltaic systems

In order to exploit as much as possible the surfaces apt for installation of photovoltaic (PV) systems and also to keep the unit energy cost low (without increasing meaningfully capital and operation/maintenance costs), fixed low concentration systems (LCPVs) can be adopted, such systems are normally based on flat mirrors. LCPVs can be either fixed or tracked, but in this paper the fixed solution is investigated as it is a solution that can be largely exploited in urban and suburban contexts, as well as it represents a retrofit of existing PV plant. In order to mitigate the negative effects of partial shadowing of such systems, together with dust soiling and mismatching, this paper proposes an innovative solution for fixed LCPVs based on Distributed Maximum Power Point Tracking (DMPPT) at substring level, here called Enhanced LCPV (E-LCPV). To evaluate the energy performance improvement of the E-LCPV solution compared with conventional LCPVs, a simulation tool has been developed; it has as input the geographic, geometrical, optical and electrical characteristics of a fixed LCPV system and provides the daily production curves. The novelty of the tool here proposed is its ability to manage non-uniform irradiance conditions on a single PV module, which allows to compare the performance of the system with or without DMPPT at substring level. Specifically, four cases have been simulated: (a) without reflector and with bypass diode (conventional PV module); (b) without reflec-tor but with DMPPT at the substring level; (c) with reflector and with bypass diode; (d) with reflector and with DMPPT at the substring level (E-LCPV). Comparative and parametric results are provided and discussed. Referring to Catania (Italy), results show that, in order to have advantages in using a E-LCPV, the PV module/reflector configuration should be accurately optimized in order to increase the power production, otherwise the cost of E-LCPVs can reduce drastically the advantages of using these kind of systems.